The Unforgivable Wars: Imperio
by Evancorsis
Summary: Harry wanted to defeat Voldemort. That was all he wanted. He really couldn't have known that accepting the aid to do so would bring about not war, but a revolution. Post-OoTP, R for a reason, Dark!Harry.
1. The Power the Dark Lord Knows Not

**Disclaimer**: I own none of the recognizable characters appearing in this story. They belong to J. K. Rowling, and I am making no profit from this fanfiction.

**Summary**: Harry wanted to defeat Voldemort. That was the only thing he wanted. He really couldn't have known that accepting the aid to do so would bring about not only war in the wizarding world, but revolution.

**Pairings**: At this point, I really don't know what pairings there might be, or if they would be het or slash. I have most parts of the plot laid out in my head, but romance is something I have to improvise. The only thing I can say with safety is that this will be a fairly lengthy story, and mostly plot-driven.

**Rating**: R for violence, gore, torture, language, and character death.

**Timing**: It begins the summer immediately after Harry Potter and the Order of the Phoenix.

The Unforgivable Wars Book One: Imperio Chapter One: The Power the Dark Lord Knows Not 

Harry Potter was used to waking from nightmares. This one was different. He woke _into _a nightmare- the pressure of sharp teeth on his right eyelid, and a voice saying, "You do not need both eyes, do you?"

Harry lay still, barely breathing. Anger might have overtaken him if he let it. Sirius gone and Voldemort back; didn't he have enough to worry about? But fear overpowered everything he might have said when the teeth shifted slowly along his eyelid, prickling and punching at the skin.

"Good," said the voice. Harry listened for breathing, but heard none. He couldn't feel breath on his face, either. He pictured a vampire crouched over him, fangs resting on his eye, and fought the temptation to be sick. _A vampire couldn't get through the wards on the house, could it? I thought Dumbledore said I was safe here..._

The voice snickered. "Not safe from us," it said. "I am not Voldemort. But we are something you should be wary of. Oh yes, Harry Potter. Very cautious. Very frightened." It giggled, a sound that reminded Harry far too much of Bellatrix Lestrange in the Department of Mysteries, and shifted to the left, so that the teeth rested mostly on his cheekbone.

Harry took a deep breath and summoned all the anger he could, then heaved himself off the bed. The thing went flying away from him with a snarl, and Harry scrambled off the bed and for the loose floorboard where he'd hidden his wand. He should have kept it by him, he scolded himself as he knelt frantically and rummaged for it. He should have-

A massive weight hit his back, pinning him to the bedroom floor and knocking the wind out of him. Harry grimaced as his mouth hit the floor and began to bleed.

"What do you _want_?" he hissed, fighting the temptation to shout. That would bring the Dursleys upstairs in a minute, and any Order members watching the house, too. Harry didn't want them there. He hadn't wanted them in his room all summer, and that wasn't about to change until he learned that he couldn't fight the thing on his back by himself.

"To help you," said the thing.

Harry laughed bitterly. "Of course you do. Why'd you bite me and try to kill me, then?" He attempted to move, but the thing seemed to grow arms and pin him down. Harry didn't bother trying to turn his head to get a good look at it. It was almost mashing his lip into the floor, too.

"I do want to kill Voldemort."

Harry looked up immediately. There was something else in front of him, but it merely prowled out of the shadows and sat watching him in the fall of moonlight from the window. It looked, Harry had to concede, like a cat, though a very large one—it would probably reach his waist if he was standing up—and with white patches on its black fur that rippled and moved strangely, as if they were patches of moonlight on the surface of the lake at Hogwarts. Harry swallowed when the cat bared its teeth. Those were the sharp things he had felt on his face, he was sure, more like needles than teeth.

"What are you?" he thought to ask, finally. Maybe that was better than asking what they wanted. Maybe they would give him an answer that made sense.

"We are me," said another voice, and a second cat came out of the shadows to his left.

"We are the ones Voldemort disturbed." A third cat was sitting to the right, though Harry hadn't seen it move. Its eyes were larger than the others', and glittered golden. "The ones he woke because he was always seeking for power, power, power." It bared its teeth and giggled just like the one on Harry's back. "And he found it. Just not the way he thought."

"I am the power the Dark Lord knows not," said a fourth voice from behind him.

"We are all the power the Dark Lord knows not," said the voice in his ear, and giggled loudly enough to hurt. Harry tried to rub his ear, and found that his arm was still pinned to the floor.

"And you just decided to show up now?" he demanded. "And why are you cats? And what the fuck is going on?" He felt a brief blaze of guilt at using the word, but then told himself he didn't bloody well care. Who was going to hear him? The Dursleys would only wake up for screams, and the Order members didn't care, and Ron and Hermione _certainly_ weren't there to hear him. Their letters had been distant and filled with vague hints. The most expansive ones he'd gotten from them were on his birthday, and they'd been only a few lines long each.

The cat on his back leaped off, and padded around in front of him. Harry still couldn't feel its breath as it leaned down and shoved its teeth near his face. "I could show you what we really look like," it said. "Unless you are frightened of me."

"No," said Harry, resenting them all fiercely. He wondered if he could get his wand and fling them across the room with a curse before they could move—

The cat vanished. In its place was intense blackness, and a searing cold, and something so horrible that Harry shut his eyes instinctively and tried to back away, slamming into something else cold as he went.

He couldn't feel anything else, as his fingers tingled and went numb in the next second. He couldn't even feel the floor anymore. He was hovering in darkness, and a wind shrieked in his ears, and someone very far away was laughing and would not stop, and something near was buzzing like a hundred flies, and—

Abruptly, the cold vanished, and Harry found himself slammed into the floor again. He opened his eyes, shaking, to find the nearest cat lying almost nose-to-nose with him. Its eyes were intensely green.

"Lie still," said the cat, almost gently. "We will tell you my story, but you must _listen_, and you must decide if you wish to make an alliance with us in all good faith."

Harry nodded shakily and rubbed his head. _What is going on? Probably just something else that Dumbledore forgot to tell me,_ he thought viciously. But he seemed stuck in the room for right now, and no one had come pounding up the stairs to save him, so he might as well listen.

Besides, a tiny—tiny—glimmer of hope was growing inside him. If these things really wanted to kill Voldemort, and Voldemort didn't know about them, then maybe they really could help him. Harry had gone almost mad this summer, lying in his bed, having nightmares about the tortures that Voldemort performed steadily, and completely unable to learn anything that might let him help. He had even written Dumbledore asking if he could come to Hogwarts early and get some kind of special training that would let him go up against Voldemort. Dumbledore had answered him, kindly but sternly, that winning the war wasn't Harry's responsibility alone, and that owls could be intercepted, so he should owl only when he truly had need, and only in code.

The green-eyed cat went on speaking, while the other four lay down, staring intensely at Harry. Harry tried to ignore the stares, though they felt like the ones aimed at his scar all the time, and fixed on the green-eyed cat. It seemed to know what it was talking about.

"Voldemort, who was once Tom Riddle, has traveled widely all over the world," the green-eyed cat began. "This much I learned about him, when we rose at last."

Harry opened his mouth, then hesitated.

"You may speak," said the cat, in a voice that reminded him almost of Professor Lupin.

Harry nodded. "Why didn't you know about him before?" he asked. "And why do you keep speaking that way?"

"What way?"

"Well—leaping back and forth between we and I," said Harry, wondering if he should have mentioned it now. It was a small thing. These creatures were willing to help him. He wanted help, didn't he?

"That is the way that I am," said the cat. "The way we all are. No difference. Do you see?"

Harry didn't, but he just gestured for the cat to keep talking.

"I did not know about him before," the cat continued, "because we had no reason to. He tampered with the Dark Arts, but that was all they were. Dark Arts, not the Darkness. Cruel little spells that you humans use against each other, and not any powers that lie in the night." Its tail flicked, once, and Harry saw its eyes change color, dancing with the moonlight. But they returned to green in the next moment, and the cat lifted its head as though it regretted having changed in any way. "Of all your spells, only the Unforgivables come close to the true Darkness, and even they have been warped and changed. So long as your Tom Riddle played in the shadows, I had no reason to wake from our slumber.

"But then he touched the Darkness. Oh, he dared." The cat hissed, and its hiss was echoed by the other four. Harry shivered, for a moment feeling that cold wind play around him. "He _dared_ to come back from beyond death, to invoke the magics of immortality that lie in the Darkness and pretend he had a right to them. No human does that. I awoke, then, and tried to kill him. But he had your blood. He has played games, this Tom Riddle, this Slytherin snake, this shadow-dancing fool." It bowed its head, and Harry had the disquieting sensation that now all the cats really were staring at his scar. "He has set up what he thinks is a private game between the two of you. Kill or be killed, is it not?"

"Yes," Harry whispered, remembering the prophecy. _And either must die at the hand of the other for neither can live while the other survives…_

The cat nodded, an oddly human gesture. "He thinks to set himself beyond any vengeance. He does not know of us, but he would break your protection and prevent anyone else from interfering in the game. I must enter the game to stop him." Its head twisted to the side, and Harry became convinced that it was going to fall off, but the neck seemed to stretch and bend, flexibly, so that the cat could look at him sideways. Of course, it wasn't really a cat, Harry reminded himself, and swallowed the queasy feeling in his stomach. "In one way, his shadow-dancing has protected him," the cat mused. "There is no place for the true Darkness in such shadows, not unless we _make_ one. I have come to make one."

It stood up, quite abruptly. Harry would have backed away, but there were the other four around him, waiting. The green-eyed one stepped forward, gaze on his scar and then on his face.

"Harry James Potter," said the cat, and Harry's skin prickled worse than it had in the cold wind of the beings' true presence. "We formally request entrance to the game."

"How?" Harry asked. His voice croaked, and he fought off the urge to wrap his arms around himself. He had to be strong. _They're offering me a deal to defeat Voldemort. They're part of the prophecy. I have to listen._

"I will enter your body," said the cat. "All of us will, turning into Darkness and passing within. Through you, I may defeat Voldemort—for though he has your blood in his veins and so has sealed himself against other enemies, he has no protection against our might passing through your hands, your eyes, your wand." It paused, and its eyes went back to Harry's scar again. "Your magic," it added in a whisper that nonetheless made the floor tremble. Harry hoped the Dursleys wouldn't wake up now. "I will give you magic, Harry, magic such as you have never dreamed."

Harry licked his lips. He wanted to. He wanted Voldemort dead, and he wanted the Death Eaters dead, and he wanted Sirius back—but that wasn't going to happen. Was it?

"I thought the Darkness wasn't for humans," he ventured.

The other cats giggled. Harry flinched. Their laughter really was too high and piercing. He wondered if he would become used to it.

"It can be, if we let it be," said the green-eyed cat. "I shall give it to you, Harry. In return, we shall live in your body, and defeat Voldemort through you."

Harry shuddered as he remembered the way that Voldemort had possessed him in the Department of Mysteries. This was the same thing, wasn't it? It had to be bad, didn't it?

"It will take some time," said the cat, as if listening to his thoughts. "But I may give you a taste of it."

It leaned forward, and touched its tongue to his scar.

Harry jumped. Quite suddenly, the room around him had vanished, and he stood in a ring of stones. He glanced about quickly. He had been here before, in dreams, and knew the barren branches of the trees that leaned over the stones. The Death Eaters killed Muggles here.

"You are quite safe, Harry," said the cat's voice beside him, and it stepped into view, its body transparent. Harry glanced down and noticed for the first time that he himself was transparent. Around him, other shadows flickered and darted, and he guessed those were the cats, moving into place. "We will protect you. And I will give you what you most want. Look ahead of you."

Harry did, and felt his heart contract. A woman had just stepped into view between the stones, smiling and mad. Bellatrix Lestrange.

"She is yours," said the cat beside him. "Do you accept our bargain, she will die screaming in agony this very night."

Harry hesitated one more time. This talk of Darkness and moving inside his body rather frightened him—

And then he saw Sirius again falling through the veil, stabbed by the red light from Bellatrix's wand.

How could he give up the chance to avenge Sirius? It was what his godfather would have done for him. Besides, wasn't he _supposed_ to accept this power? They were "the power the Dark Lord knows not." They were part of the prophecy.

Bellatrix Lestrange laughed, just the way she had after she killed Sirius, at something another Death Eater behind her had said, and Harry made up his mind.

"Yes," he murmured, unable to take his eyes from her. "Oh, yes."

There came one more chorus of shrill giggles, and the green-eyed cat's voice said, soothing and low, "You shall not regret this, Harry James Potter. So the bargain is sealed. _Tenebrae_!"

And the Darkness came into Harry.


	2. The Destruction of Bellatrix Black Lestr...

**Warning: **This chapter contains graphic gore. Sensitive readers take note. Also, Harry is very definitely not himself right at first.

**Chapter Two: The Destruction of Bellatrix Black Lestrange**

It was night.

Harry _knew_ that, now, as he had never known it before. The sun wasn't above the world. Darkness was. It was only a pale copy of the glory to be found in the night behind the stars, below the earth, in the depths of _them_, for the sun would rise again. But it was night, and that was a joy and a pride and a comfort.

He looked at the two Death Eaters before him. Both women. The one speaking to Bellatrix was a woman he didn't know, but with the sneering lip and haughty tone of a pureblood. Harry could feel the Dark Mark on her arm. A pitiful effort of Shadow magic, truly, but closer to the true Darkness than most. Harry supposed he could admire that.

The other…

The other was Bellatrix, and at that moment Harry came fully into the place where the Death Eaters stood, and she saw him.

Her eyes widened, and a high shriek escaped her lips. Harry didn't wait to see if it was going to be laughter. His mind was full of veils and red light and falling godfathers, as it had been for every night of the summer. His sight multiplied and swam, until it seemed as if he were looking at Bellatrix through five pairs of eyes, and the Darkness rose up in him and roared like the night.

Harry held out a hand and gestured once. The five visions in front of him snapped back into one again, and he was able to see—though he didn't know if Bellatrix was—the long tendril of black that crept from his arm and towards her. It would drown the stars forever, and swallow the light of _Avada Kedavra_. It was magic that Voldemort would have killed to possess and Dumbledore would have paled to see.

The blackness touched Bellatrix and curled almost lovingly around her, fast and fluid.

The next moment, she screamed, and this time it was definitely a scream. Harry walked forward, smiling. He could feel that he was smiling, and yet it felt strange to do it. One part of him had never imagined smiling at something like this. The other was unused to human skin, and unsure if it had the muscles correct.

"Did you lose something?" he asked her. His voice was his own, still.

The tendril had enclosed her whole body, but was thickest around her left arm. Bellatrix didn't answer in words, just screamed again. Beyond her, the other Death Eater woman backed away fast enough to slam her shoulders into one of the stones, then turned and ran into the night.

Harry cocked his head, and waited.

The tendril drew away at last, and Harry blinked to see Bellatrix's arm still unaffected. _She_ didn't seem to notice, panting in pain as she was, but that wasn't enough.

_I thought you said_— 

_Wait for a moment,_ whispered the Darkness's voice, within, inside, around him. Harry shuddered. It sounded as if it had spiraled out of the middle of his spine, actually. _Now, sniff the air._

Harry did, and noticed the putrid, rotting smell then. He watched in fascination as Bellatrix's arm turned soft, the flesh becoming black and spongy. It ripped down the middle, then separated into twin sheaths of mold, falling and peeling from the muscle. Then the muscle followed, a rain of reeking slime. In a few moments, Bellatrix had nothing in place of her left arm but a bone, and that yellowed as Harry watched, blackened, and blew to dust.

Harry shuddered, once, and a surge of immense satisfaction flooded him. He found that Sirius's image, when he recalled it, seemed fainter than before.

_Do you understand? _the Darkness whispered to him. _I have power over life and death. And more than that. Other things. Things that spells cannot do. We can strengthen your magic, or I can punish her in ways that Voldemort has not dreamed of._

_I would like that, _said Harry, with the part of him that found wearing human skin unusual, and human words confining for what he really meant.

Bellatrix was screaming, he realized as he came back to himself. She had probably been screaming for some time, but he hadn't heard it, so focused on his own handiwork was he.

"Quiet," Harry said.

And she was quiet, as her tongue slipped rotting from her lips and to the forest floor. Harry looked into her eyes. She was mad from Azkaban, he knew, but now she was truly mad. He didn't know if any sanity was left behind those shrieking eyes.

"I want her to know what she did to me," he said aloud. It felt unnatural, yes, but it also felt as if he knew what was Darkness and what was Harry more easily that way. "I want her to feel it."

_Easily enough arranged_, said the Darkness, in the green-eyed cat's voice. _At bottom, all darkness is connected. We are night. I am dreams. In your dreams is enough pain to encompass her. Be it so._

This time, Harry couldn't see the black tendril at first, but felt it as a pendant drop of sweat, suspended between his eyes. He blinked and shook his head, and it oozed out. It seemed to take a long time to fall, even then. Harry wrinkled his nose when it finally hit the ground. It shimmered with the shades of Muggle petrol, and it was viscous enough to take long moments to work its way to Bellatrix.

"What is it?" he whispered.

_That is your grief,_ said the green-eyed cat. _That is your pain at the loss of your godfather. That is what you have felt because of her._ Shrill giggles sounded in Harry's ears as he watched the drop trace its way over to Bellatrix and climb up her knees to her face. _She will feel everything that you have felt, _the Darkness continued, in a dreamy fashion. _Little shadow-dancer. Let her look into us, and see if she still relishes the thought of following the one who dares to name himself Dark Lord._

The grief had touched Bellatrix's jaw by now. It turned in a circle like a tiny snake, then sank into her eyes. Harry found himself leaning forward, wondering what would happen. He had taken away her tongue. Would she continue screaming? Would he see any change?

Bellatrix shuddered, once, and then looked up at him.

What Harry saw there was what he had seen reflected in his own eyes, night after night, as he stared into his mirror in a desperate attempt to convince himself to go back to sleep. Pain, anguish, defeat, despair, helplessness. Emotions that Harry had thought, until he saw the color of the drop that had put them in Bellatrix's eyes, were the blackest things in the world.

Bellatrix began to weep.

Harry, who could not even have imagined the sight, drew a long sigh and sat on the ground. He watched as she cried, and the cats watched with him. Harry could almost feel them as separate personalities again, sliding and fluid, sometimes nudging about as though they wanted to investigate his stomach or his legs. Luckily, they had calmed down by the time Bellatrix ceased to rock back and forth and simply stared blankly in front of her, because Harry wanted to know what to do next.

_Do you wish her to die?_ another voice asked. Harry thought it was the golden-eyed cat this time, the one who had seemed slightly more dignified than all the rest. It sounded like what Lucius Malfoy might have been, had he ever achieved true elegance.

"I do," said Harry. "I've made her suffer, and I've made her scream in agony. I think I want her to die."

_Then watch me,_ said the golden-eyed one's voice. _Lift your hand and hold it forward. We will teach you to cause death by causing life._

Harry cocked his head, curious, and held his hand out. He rotated it so that the palm faced Bellatrix, at the cats' brief instruction, and then bent his second and fourth finger inwards. The Darkness did not need the gestures, but they were the best approximation of what it would normally do while it was in Harry's body.

Bellatrix gasped and arched off the ground slightly. Harry could feel her heart beating like a small, frightened thing under his palm.

"What did you do?" he whispered.

_Watch._

Harry did, and noticed that the beat under his palm was getting stronger and stronger, faster and faster. Bellatrix was gasping in time with it now, her one remaining hand rising to her chest, her lips fluttering as though she would sing a tune.

The heartbeat rose until it sounded like music. It was, in a way, Harry thought through a gentle haze, the music of life, the music that turned a human's life into time.

Time spiraled faster and faster for Bellatrix Black Lestrange, and then it exploded.

Harry blinked and looked at the motionless body slumped in front of him. Dawn was coming, and he was sitting in the scattered leaf-litter of a stone circle where the Death Eaters killed Muggles, and Sirius's murderer had just died of a broken heart.

Harry began to laugh. He wasn't sure what he found funny, and he was still wheezing when the clearing vanished from around him and he sat in his bedroom in Privet Drive again. Light crept through the window, and he slumped forward like Bellatrix had, laughing until his chest hurt.

The Darkness drew back slightly.

And the knowledge of what he had just done rushed in on Harry.

He would have screamed, but that would let the Dursleys know he was up, and he couldn't have that, not just yet. Overwhelmed, he leaned forward instead and let his head fall into his hands. His breath was fast enough to hurt his throat as the laughter hadn't. He wanted to weep, but at the same time, what he had done was so far beyond weeping that he couldn't manage it.

"What did I do to her?" he murmured.

"Caused her exactly the pain that she caused you."

Harry jerked his head up. For some reason, he had imagined that Dumbledore said that last, and that the Headmaster would be sitting in the room with him. Harry didn't think he could bear to meet the older man's gaze just at the moment. But, instead, it was the golden-eyed cat, who sat beside him and reached out a paw when Harry stared at it. The paw rested lightly on his arm. Harry stared down at the claws in turn. They looked sharp enough to tear someone's face off, but they didn't break his skin.

"I know it," said the golden-eyed cat. "She suffered as you did. No more, and no less."

"But her arm, and her heart…" Harry said, and then shook his head. His voice was hoarse and thick with tears. He wouldn't have understood himself if he didn't know what he said.

"Matched the pain of the _Crucio_ spells that she has cast," said the cat. Its eyes understood, but did not pity, either him or Bellatrix. "No more, and no less."

"How can you be sure of that?"

"Because the Unforgivable Curses are the most powerful of your vicious little spells, the closest to true Darkness, as we told you," said the cat. It leaned closer to him, and Harry felt a little shock of warmth as its head rubbed against his chest. He hadn't thought the cats would be warm., but cold as the wind that blew around him when they showed him their true forms. "I can feel them. We can feel when they are used, and when I look at a Death Eater, we can tell how much pain they have caused. I can feed that pain back into the Death Eater. We can make them suffer for what they did."

"But that's not justice," Harry whispered. Dumbledore's voice was echoing in his mind, the words he'd spoken at the end of second year. _It is our choices which make us who we really are…_

Harry shivered again. _What kind of a choice have I made?_

"A good one," said the cat, and Harry started slightly. "And no, it is not justice, nor is it mercy. It is balance. The Unforgivable Curses cause command or pain or death to hover around the person who casts them. They are the darkest part of the shadows that I see. It is a simple matter to push the balance back to true, as we did."

"What if I don't want this?" Harry asked. "What if I changed my mind, and told you all to go away?"

"It would disappoint me very much," said the golden-eyed cat.

"But you wouldn't take revenge on me?" Harry remembered the way that Bellatrix's arm had turned black, and shivered. _No,_ he told himself. _I have to be strong. I'm brave. I'm a Gryffindor._

That didn't stop the memory from terrifying him anyway.

"We cannot," said the cat, its voice rueful. "You are my only entrance to the game. We must have you intact, your blood and mind and magic intact, or I cannot face Voldemort and punish him for what he has done."

Harry thought about that, and what the cat had said about balance, and something went _click_ in his head. "That's why you didn't just go and punish Voldemort right away," he said. "He's caused so much pain and death…"

"It will take a long time to set the balance back to true," said the cat. "Oh, yes. It will take a _very_ long time." Its eyes shone in the sunlight, so brilliantly that Harry had to look away. "This was the first step. But it will take many more." It butted its head on his chest again, and Harry looked down to find it still staring at him. "We must have you to do it."

"It will end the war?" Harry asked, hovering on the very last vestiges of his resistance.

"Yes. It will assure the prophecy," said the cat, with absolute certainty. "I cannot know how it would fall out without us. You might survive. But with me, you certainly will. And when we have punished Riddle, the pale, sniveling shadow of a snake, then I will depart. You have our word."

Harry shuddered, once, and then nodded.

"You accept?" the cat said.

"I have to," Harry whispered back. It was horrible, but he had to. He was thinking of the Muggles he had watched die so far this summer, four Muggle families altogether. Ron and Hermione, and how they would suffer for being Harry's friends. Snape, holding his left arm in fourth year. His father and mother, dying to save him.

And Sirius. Always, first and last and at the end, Sirius.

_If I had had this power before, how many deaths could I have prevented?_

The guilt was an old, familiar friend, but this time, it was lessened by the warmth of the cat against him. After a moment, the great animal began to purr, steadily.

Harry put an arm around it.

"You may call me Sirrmonsiir," said the cat at last, opening its golden eyes and blinking them at Harry. "In no tongue humans ever spoke, it means _solace._ Call the name when you have need of that part of us, and I shall answer."

Harry nodded, and the cat wafted into Darkness and back into him. He felt a faint gliding sensation against his neck, and then mental and physical silence.

It was a strange sensation, to sit on his bedroom floor in the morning light and know that the war with Voldemort would end, decisively, in his favor, no matter how much pain he had to cause to do it.

But Harry thought he could get used to it.


End file.
